1. Technical Field
The invention relates to the art of tire inflation systems. More particularly, the invention relates to tire inflation systems for heavy-duty vehicles such as tractor-trailers or semi-trailers, which can operate as the vehicles are moving. Still more particularly, the invention is directed to a tire inflation system which incorporates an electrical or mechanical pump that increases the air pressure that is available to the tire inflation system, and in which the pump is connected to the tire inflation system in a manner that is separate from and pneumatically parallel to the vehicle air supply, thereby enabling the pump to operate independently of the vehicle air supply.
2. Background Art
All tractor-trailers include at least one trailer, and sometimes two or three trailers, all of which are pulled by a single tractor. Each trailer typically includes multiple tires, each of which is inflated with air to a recommended pressure. However, it is well known that air may leak from a tire, usually in a gradual manner, but sometimes rapidly if there is a problem with the tire, such as a defect or a puncture caused by a road hazard. As a result, it is necessary to regularly check the air pressure in each tire to ensure that the tires are not under-inflated. Should an air check show that a tire is under-inflated, it is desirable to enable air to flow into the tire to return it to an optimum tire pressure.
The large number of tires on any given trailer setup makes it difficult to manually check and maintain the optimum tire pressure for each and every tire. This difficulty is compounded by the fact that multiple trailers in a fleet may be located at a site for an extended period of time, during which the tire pressure might not be checked. Any one of these trailers might be placed into service at a moment's notice, leading to the possibility of operation with under-inflated tires. Such operation may increase the chance of failure of a tire in service as compared to operation with tires in an optimum inflation range.
Moreover, should a tire develop a leak, for example, as a result of striking a road hazard, the tire could fail if the leak continues unabated as the vehicle travels over-the-road. The potential for tire failure often is more pronounced in vehicles such as tractor-trailers that travel for long distances and/or extended periods of time.
Such a need to maintain optimum tire pressure, and the inconvenience to the vehicle operator to manually check and maintain proper tire pressure, led to the development of prior art systems that attempt to automatically monitor the pressure in a vehicle tire and/or inflate the vehicle tire with air to a desired tire pressure as the vehicle is moving. An exemplary tire inflation system of the prior art is shown and described in U.S. Pat. No. 7,273,082, which is owned by the assignee of the present invention, Hendrickson USA, L.L.C.
Prior art tire inflation systems generally involve providing air from the air supply of the vehicle to the vehicle tires using a variety of different structures, arrangements and/or methods. While being satisfactory for their intended functions, tire inflation systems of the prior art may experience disadvantages in certain situations. More particularly, in some systems, the air pressure that is required to inflate a tire may be greater than the pressure capacity of the vehicle air supply. This situation is sometimes experienced in geographic areas such as Europe, where tires with higher inflation pressures are often employed. As a result, in cases where the air pressure that is required for the tire, and thus the tire inflation system, is greater than the pressure capacity of the vehicle air supply, it is necessary to increase the pneumatic pressure that is available to the tire inflation system.
A prior art solution to the need to increase the pressure for the tire inflation system has been to provide an in-line booster pump. More specifically, in such a system, the inlet of a booster pump is connected to the outlet of the vehicle air supply. The booster pump thus takes the compressed air from the vehicle supply and boosts the pressure of the air from the vehicle supply to a higher level. Such a system is considered to be an in-line system, because the inlet of the booster pump is pneumatically in-line with and is connected to the vehicle air supply.
While the prior art in-line booster pump system does increase the air pressure that is available to the tire inflation system, it possesses certain disadvantages. For example, the in-line booster pump depends on the vehicle air supply, since the pump does not provide an independent source of air. Thus, if there is a malfunction of components associated with the vehicle air supply, the booster pump is not independently able to provide air to the tire inflation system. Also, since the in-line booster pump is located directly between the vehicle air supply and the remainder of the tire inflation system, a malfunction of the booster pump may undesirably block or otherwise affect the supply of air to the tire inflation system from the vehicle air supply. Moreover, since the in-line booster pump is located directly in-line with the vehicle air supply and other tire inflation system components, a significant amount of time may undesirably be required to disassemble and reassemble system components when it is necessary to service or replace the booster pump. In addition, in the event of failure of the in-line booster pump under conditions in which proper servicing and/or replacement of the booster pump is not available, it may be inconvenient and/or expensive to bypass the pump.
As a result, there is a need in the art for a tire inflation system that provides a pump or compressor which is pneumatically separate from and parallel to the vehicle air supply, rather than being pneumatically in-line with the vehicle air supply. Such a pneumatically parallel pump should operate independently from the vehicle air supply, thereby enabling: the pump to provide air to the tire inflation system in the event that components associated with the vehicle air supply malfunction; the vehicle air supply to provide air to the tire inflation system in the event of malfunction of the pump; easy servicing and/or replacement of the pump; and easy bypassing of the pump, in the event that such a bypass is needed. The tire inflation system with parallel pump of the present invention satisfies this need, as will be described in detail below.